Conventional apparatus for washing, dehydrating and/or classifying particulate solids comprises a reservoir or feed chamber which receives a slurry comprising water or other washing liquid and the particulate solids. The solids, for example, may be sand, crushed rock fines, industrial minerals, metallic ores, coal or metal chips etc. As will be apparent, the particulate solids settle downwardly in the liquid in the reservoir or feed chamber and are then conveyed upwardly along an inclined path by the rotating helicoid of a screw conveyor. During the upward travel of the solid particulate, the solids emerge above the surface of the liquid permitting liquid drainage by gravity from the solids during their continuing upward movement to a discharge outlet at the upper end of the screw conveyor.
The upper end of the screw conveyor may have its shaft supported by a conventional roller bearing and may be driven by conventional means such as an electric motor. The lower end of the conveyor shaft is submerged in the liquid and may be journalled in a sealed outboard roller bearing or a pressurized liquid flushed marine type bearing similar to those used with boat propeller shafts.
Due to turbulence within the liquid slurry, conventional submerged and sealed bearings require regular inspection and may frequently require replacement of seals which wear as a result of the gradual and unavoidable ingress of abrasive solids. Where pressurized water flushed bearings are used, any temporary curtailment of flushing water as from a drop in water pressure may result in the intrusion of abrasive solids into the bearing assembly, thereby accelerating wear and the need for replacement.
It is the general object of the present invention to provide a liquid lubricated bearing assembly for use in a washer, dehydrator, classifier or other apparatus, the need for elaborate sealing or the use of external flushing water or other liquid being eliminated, and yet highly efficient operation and long life of the bearing assembly being achieved.
In accordance with the present invention and in fulfillment of the foregoing object, a self cleaning bearing assembly is provided for use in a dehydrator, washer or the like for fine particulate solids having a feed reservoir into which liquid and particulate solids are received and an inclined screw conveyor with a lower end portion and a projecting shaft end portion submerged in the reservoir. Communication of the bearing housing with the interior of the washer reservoir preferably occurs at a location above the lowermost point of the reservoir. The bearing housing longitudinal centerline is coincident with the axis of the main screw conveyor and its shaft and a stub shaft mounted on the end cap of the bearing assembly housing also has its axis coincident with that of the screw conveyor and its shaft. The projecting lower end portion of the conveyor shaft and the stub shaft are disposed one within the other in radially spaced relationship and a conventional sleeve bearing is disposed in the radial space between the stub shaft and the projecting end portion of the main conveyor shaft. A short auxiliary helicoid conveyor section disposed in the bearing housing acts to efficiently sweep abrasive solids away from the sleeve bearing whereby to maintain the same in a clean condition for lubrication by the liquid in the reservoir.
In accordance with the presently preferred practice, the short auxiliary screw conveyor section is mounted on and rotatably driven by the projecting end portion of the main conveyor shaft. The pitch of the auxiliary conveyor section, however, is substantially less than that of the main conveyor to provide for relatively high frequency or high velocity upward sweeping movement of solids which may enter the bearing housing. Finally, the shaft of the main conveyor is preferably tubular with the stub shaft disposed therewithin and the short auxiliary screw conveyor section mounted on the exterior of the shaft.
In a general purpose embodiment of the bearing assembly, a shaft end portion is submerged in a liquid which may or may not have fine particulate solids also submerged in the liquid, but which may have other potential bearing contaminants requiring flushing of the bearing assembly. Accordingly, a short auxiliary screw conveyor section as described is provided for such purpose in the liquid and acts to sweep potential contaminants away from the bearing as aforesaid.